Effect of Drum Drying Process on the Physico-Chemical and Antioxidant Activities of Riceberry Flakes

Abstract

Abstract. Pigmented rice, such as black or red rice, contains several antioxidant compounds. Riceberry rice, which is native to Thailand, is a colored rice variety that is rich in bioactive constituents. With several benefits from the anthocyanin and phenolic compounds in Riceberry rice, value-added products have been developed, for which the physico-chemical and mechanical properties need to be studied. This study evaluated the effects of drum drying parameters on the physico-chemical properties and bioactive compounds of Riceberry flakes. Three drum surface temperatures (130°C, 140°C, and 150°C) and three solids contents of flour slurry (35%, 45%, and 55%) were applied. Lightness (L*) of the flakes significantly decreased (p < 0.05) while redness (a*) increased compared to the flour. Bulk density, hardness, and water solubility index of the flakes increased with increasing drum temperature and solids content. The highest values were found at drum temperature of 150°Cand55% solids content.Major anthocyanins in Riceberry flour and flakes were cyanidin-3-glucoside and peonidin-3-glucoside.Total phenolic content, flavonoid content, and antioxidant activities of Riceberry flakes decreased during drum drying. The highest drum temperature (150°C) and solids content (55%) of flour slurry gave maximum contents of bioactive compounds. Results suggest that Riceberry flakes can be used as a functional ingredient for food products. Keywords: Breakfast cereal flakes, Drum drying, Riceberry rice, Rice flakes.